Wind Turbine Blade Comprising Root End Bulkhead

ABSTRACT

A wind turbine blade ( 10 ) for a rotor of a wind turbine ( 2 ) having a substantially horizontal rotor shaft is disclosed. The rotor comprises a hub ( 8 ), from which the blade ( 10 ) extends substantially in a radial direction when mounted to the hub ( 8 ), the blade having a longitudinal direction (r) with a tip end ( 16 ) and a root end ( 14 ) and a transverse direction. The wind turbine blade comprises a blade shell defining a profiled contour of the blade and having an inner shell wall, wherein the blade is provided with a bulkhead mounted to the inner shell wall at the root end of the blade via an attachment part, the bulkhead comprising a first side and a second side. The attachment part is integrally formed with or connected to the bulkhead, and the attachment part comprises an elastomeric material.

TECHNICAL FIELD

The present invention relates to a wind turbine blade for a rotor of awind turbine having a substantially horizontal rotor shaft, said rotorcomprising a hub, from which the blade extends substantially in a radialdirection when mounted to the hub, the blade having a longitudinaldirection with a tip end and a root end and a transverse direction, thewind turbine blade comprising a blade shell defining a profiled contourof the blade and having an inner shell wall, wherein the blade isprovided with a bulkhead mounted to the inner shell wall at the root endof the blade via an attachment part, the bulkhead comprising a firstside and a second side. The invention also relates to a method ofmanufacturing a bulkhead and attachment part combination.

BACKGROUND

A modern wind turbine comprises a rotor having a hub and a plurality ofwind turbine blades, which extend substantially radially from the hub.The rotor is mounted to a machine housing or a nacelle, which in turn isarranged on top of a tower. The machine housing can yaw so that it canpivot around a vertical shaft in relation to the tower, hereby beingable to adjust the rotor to the direction of the wind. The rotor can beput into rotation by the wind, thereby driving one or more generators.

Wind turbine blades are often provided with a bulkhead arranged at aroot end of the blade, typically located within the inboard 20% of theblade. The bulkhead has two functions. First of all, it functions as awork platform for workers when having to carry out maintenance or repairinside the blade. Second of all, it prevents internal debris fromfalling into the machine housing of the blade. Additionally, whenmounted expediently, the bulkhead is watertight.

The bulkhead is typically glued directly on to an inner wall of the windturbine blade. However, a wind turbine blade is subjected to large loadsduring operation, which causes the inboard part of the blade to ovalise.This in turn entails loads to the glue bonding, and in worst case thebulkhead may be torn loose from the inner blade wall. It is alsowell-known to mount the bulkhead on a bathtub-shaped flange made ofsteel or a fibre-reinforced composite material, which allows for smallmovements of the blade wall relative to the bulkhead. Such a solution isfor instance known from WO09/085041. However, this solution is alsoencumbered by large loads to the flange and to the glue bonding betweenthe flange and the inner blade wall. Further, the relatively stiffflange makes it difficult and tedious to mount the bulkhead and flangeinside the wind turbine blade.

DISCLOSURE OF THE INVENTION

It is an object of the invention to obtain a wind turbine blade, whichovercomes or ameliorates at least one of the disadvantages of the priorart or which provides a useful alternative.

According to a first aspect, the invention provides a wind turbine bladeprovided with a bulkhead, where the attachment part of the bulkhead isintegrally formed with or connected to the bulkhead part, and whereinthe attachment part comprises an elastomeric material.

The bulkhead together with the attachment part may thus be mounted inthe wind turbine blade as a unitary element. The elastomeric attachmentpart provides easy handling when mounting the bulkhead in the blade,since the material is flexible to a degree that the attachment part maybe folded into the opening of the blade root and adhered to the innerwall. At the same time the attachment part still provides excellentstrength to carry the bulkhead. Further, the elastomeric materialprovides enough flexibility to counteract ovalisation of the blade rootwithout the attachment part being torn loose from the blade wall.

According to an advantageous embodiment, the attachment part and thebulkhead together seal the root end of the blade. Thus, the bulkheadtogether with the attachment part may be mounted in the wind turbine asa unitary element, thus sealing the root end of the blade andconsequently preventing debris from entering the machine housing.Further, this solution is particularly simple for making the bulkheadand attachment part combination watertight.

According to a first embodiment, an outer diameter of the attachmentpart is equal to or larger than an inner diameter of the inner shellwall. Thus, it is ensured that the elastomeric attachment part is notpre-stressed away from the inner blade wall. At the same time theelastomeric material ensures that the attachment part and bulkheadeasily can be mounted within the blade, since the flexible attachmentpart can be folded into the blade and adhered or otherwise be anchoredto the inner blade wall of the blade. The outer diameter of theattachment part may for instance be at least 1 cm, or at least 2 cmlarger than the inner diameter. According to an alternative embodiment,the outer diameter of the attachment part is smaller than the innerdiameter of the inner shell wall, e.g. at least 1 cm, or 2 cm, or 3 cm,or 4 cm, or 5 cm smaller. Thereby, the bulkhead and attachment part maybe inserted more easily into the blade and the elastomeric part of theattachment part ensures that the attachment part can be flexed andattached to the blade wall.

According to one advantageous embodiment, the bulkhead comprises acircumference, and the attachment part comprises a blade wall anchoringpart and a bulkhead anchoring part attached to the circumference of thebulkhead. Advantageously, the attachment part is circumferentiallyattached to the bulkhead so that the two parts together seal the root ofthe wind turbine blade. Accordingly, the attachment part is connected tothe bulkhead along the entire circumference or rim of the bulkhead.

In another advantageous embodiment, the blade wall anchoring part andthe bulkhead anchoring part are separated by an intermediate part, suchas an intermediate arm. The intermediate part allows for furthermovement of the bulkhead relative to the inner blade wall or vice versa.

In a first embodiment, the blade wall anchoring part, the bulkheadanchoring part and the bulkhead are arranged substantially in the sameplane. Thus, if the attachment part comprises a connection arm, this armextends substantially normally to the inner shell wall.

According to another embodiment, the blade wall anchoring part and thebulkhead anchoring part are displaced along the longitudinal directionof the blade. Thereby, the attachment part is able to provide strengthin the longitudinal direction and thus to carry several hundreds ofkilograms, which is necessary in order to be able to carry the bulkheaditself as well as a platform or worker standing on the bulkhead.

The blade wall anchoring part and the bulkhead anchoring part may forinstance be displaced at least 5 cm along the longitudinal direction ofthe blade, or at least 7.5 cm, or at least 10 cm.

According to another embodiment, the bulkhead is displaced at least 2 cmfrom the inner blade wall, or at least 2.5 cm, or at least 3 cm, or atleast 4 cm, or at least 6 cm, when the blade is in a non-ovalised state.Thus, when mounted inside the blade, the blade wall anchoring part andthe bulkhead anchoring part are displaced equivalently in a transversedirection of the blade.

By letting the blade wall anchoring part and bulkhead anchoring partbeing displaced both in the longitudinal direction of the blade and fromthe inner blade wall, i.e. in a radial direction of the circularcross-section of the root, the elastomeric part of the attachment partis able to take up forces from the ovalisation of the root as well asprovide the necessary longitudinal or axial strength to carry thebulkhead and a worker standing on the bulkhead.

According to an advantageous embodiment, the connection arm forms anangle with the inner blade wall, the angle lying in an interval of 10 to80 degrees, advantageously between 10 and 60 degrees, and moreadvantageously between 10 and 45 degrees, e.g. around 30 degrees.

In another advantageous embodiment, the connection arm is orientedsubstantially parallel to the longitudinal direction of the blade.

Advantageously, the attachment part comprises a bulkhead anchoring partcomprising a substantially c-shaped or u-shaped part having a first partattached to the first side of the bulkhead and a second part attached tothe second side of the bulkhead. The bulkhead anchoring part may furthercomprise a third part attached to the circumference of the bulkhead.Alternatively, the bulkhead anchoring part may be anchored to thebulkhead with an air gap between the third part of the bulkheadanchoring part and the circumference of the bulkhead.

The attachment part may be anchored to the bulkhead and blade wall invarious ways, e.g. by adhesion, moulding integrally or onto thebulkhead, or via fastening means.

In another advantageous embodiment, the bulkhead comprises acircumferential groove and the attachment part is attached to thegroove, e.g. via a tongue.

In yet another advantageous embodiment, the bulkhead is formed as asandwich construction, advantageously comprising a first fibrereinforced skin at the first side of the bulkhead, a second fibrereinforced skin at the second side of the bulkhead, and a core materialbetween the first skin and the second skin. Thus, the bulkhead maycomprise a first layer of fibre-reinforced material at the first side ofthe bulkhead and a second layer of fibre-reinforced material at thesecond side of the bulkhead. The fibres may for instance be glass orcarbon fibres. The core material may for instance be made of a polymermaterial, such as a foamed polymer.

In one advantageous embodiment, the elastomeric material of theattachment part and the polymer material of the bulkhead are compatible,preferably chemically compatible. Thereby, the attachment part may forinstance be moulded onto the circumference of the bulkhead andchemically bond and adhere to the core material of the sandwichstructure of the bulkhead.

In one embodiment, the elastomeric material and the foamed polymer is apolyurethane based material. The resin of the moulded bulkhead may alsobe a polyurethane based material. Polyurethane is a very versatilematerial, where the hardness (or flexibility) easily can be varied inorder to for instance provide rigid anchoring parts and core of thesandwich structure, as well as a flexible, elastomeric intermediate partof the attachment part.

In another embodiment, the attachment part comprises a circumferentialhollow part between the inner blade wall and the bulkhead. The hollowpart may provide the necessary movement of the bulkhead in for instanceembodiments, where the two anchoring parts are arranged in the sameplane.

In yet another embodiment, the attachment part comprises acircumferential core part. The circumferential core part may forinstance be made of a material, which is adapted to pulverise orotherwise break apart when subjected to loads. Thereby, the core willbreak down during operation of the wind turbine and thus form acircumferential hollow part. The core part is thus only utilised forobtaining a form-stable shape during manufacture (and subsequentmounting) of the attachment part and bulkhead.

According to an advantageous embodiment, the attachment part comprisesan elastomeric part and a non-elastomeric part, advantageously both madeof polyurethane. The elastomeric part of the blade may for instance beattached to the inner blade wall, and the non-elastomeric part isattached to the bulkhead.

In another advantageous embodiment, the attachment part comprises agradual transition from an elastomeric material to a non-elastomericmaterial. The gradual transition may for instance be located in theaforementioned connection arm.

In yet another advantageous embodiment, the attachment part comprises asubstantially uniform ring having a thickness of at least 5 cm, or atleast 7 cm, or at least 10 cm. The thickness is defined as the distancebetween the outer diameter and the inner diameter of the uniform ring.The elastomer material of the uniform ring may for example have adurometer value lying in an interval from 10-50 on the Shore A scale,and/or have a density lying in an interval from 100-700 kg/m3.

According to another advantageous embodiment, the elastomeric materialhas a durometer value lying in an interval from 50-100, or 50-90, or55-85 on the Shore A scale. These durometer values are particularlysuitable for the embodiment comprising an intermediate part between theblade anchoring part and the bulkhead anchoring part. In anotheradvantageous embodiment, the elastomeric material has a durometer valuelying in an interval from 10-50, or 12-40, or 15-30 on the Shore Dscale.

According to a second aspect, the invention also provides a bulkhead andattachment part combination for a wind turbine blade as described in anyof the aforementioned embodiments. Thus, the invention provides abulkhead for mounting to the inner shell wall at the root end of a windturbine blade comprising an attachment part which is integrally formedwith or connected to the bulkhead, and in that the attachment partcomprises an elastomeric material.

According to a third aspect, the invention provides a method ofmanufacturing a bulkhead and attachment part, wherein the methodcomprises the steps of: a) manufacturing a bulkhead, b) manufacturing anattachment part, and c) anchoring the attachment part to the bulkhead.

In a first advantageous embodiment, the bulkhead and attachment part areintegrally formed. Accordingly, steps a), b) and c) may be carried outsimultaneously.

In another advantageous embodiment, the attachment part is moulded on tothe bulkhead, e.g. to a circumference of the bulkhead. Thus, step a) canbe carried out first and steps b) and c) simultaneously afterwards.Alternatively, the attachment part may be anchored to the bulkhead byadhesion or the like.

In one embodiment, the bulkhead is first manufactured, e.g. as a plate,then shaped and finally arranged in a mould so as to mould theattachment part on to the bulkhead. The bulkhead may for instance bemanufactured as a sandwich construction comprising a core material madeof a polymer material. The bulkhead may be made as a large plate andsubsequently be cut to the intended shape so as to be able to fit intothe root of the blade.

In another embodiment, the elastomeric material of the attachment partand the core material of the bulkhead are compatible, e.g. chemicallycompatible.

The bulkhead may be provided with a hatch so that a worker may accessthe blade, when the bulkhead and attachment part are mounted in theblade.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is explained in detail below with reference to embodimentsshown in the drawings, in which

FIG. 1 shows a wind turbine,

FIG. 2 shows a schematic view of a wind turbine blade according to theinvention, and

FIGS. 3-17 show various embodiments of bulkhead and attachment partcombinations according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates a conventional modern upwind wind turbine accordingto the so-called “Danish concept” with a tower 4, a nacelle 6 and arotor with a substantially horizontal rotor shaft. The rotor includes ahub 8 and three blades 10 extending radially from the hub 8, each havinga blade root 16 nearest the hub and a blade tip 14 furthest from the hub8. The rotor has a radius denoted R.

FIG. 2 shows a schematic view of a first embodiment of a wind turbineblade 10 according to the invention. The wind turbine blade 10 has theshape of a conventional wind turbine blade and comprises a root region30 closest to the hub, a profiled or an airfoil region 34 furthest awayfrom the hub and a transition region 32 between the root region 30 andthe airfoil region 34. The blade 10 comprises a leading edge 18 facingthe direction of rotation of the blade 10, when the blade is mounted onthe hub, and a trailing edge 20 facing the opposite direction of theleading edge 18.

The airfoil region 34 (also called the profiled region) has an ideal oralmost ideal blade shape with respect to generating lift, whereas theroot region 30 due to structural considerations has a substantiallycircular or elliptical cross-section, which for instance makes it easierand safer to mount the blade 10 to the hub. The diameter (or the chord)of the root region 30 may be constant along the entire root area 30. Thetransition region 32 has a transitional profile gradually changing fromthe circular or elliptical shape of the root region 30 to the airfoilprofile of the airfoil region 34. The chord length of the transitionregion 32 typically increases with increasing distance r from the hub.The airfoil region 34 has an airfoil profile with a chord extendingbetween the leading edge 18 and the trailing edge 20 of the blade 10.The width of the chord decreases with increasing distance r from thehub.

A shoulder 36 of the blade 10 is defined as the position, where theblade 10 has its largest chord length. The shoulder 36 is typicallyprovided at the boundary between the transition region 32 and theairfoil region 34.

It should be noted that the chords of different sections of the bladenormally do not lie in a common plane, since the blade may be twistedand/or curved (i.e. pre-bent), thus providing the chord plane with acorrespondingly twisted and/or curved course, this being most often thecase in order to compensate for the local velocity of the blade beingdependent on the radius from the hub.

It can be seen that the blade 10 is also provided with a bulkhead andattachment part combination 40 positioned in the root region 30 of theblade 10 and attached to an inner shell wall 25 of the blade 10. Thebulkhead and attachment part combination 40 has two functions. First ofall, it keeps internal debris from falling into the machine housing ofthe blade. Second of all, it functions as a work platform for workerswhen having to carry out maintenance or repair inside the blade.Therefore, the bulkhead is also provided with a hatch or manhole (notshown), which can be opened so that a worker can gain access to theinside of the blade 10.

FIG. 3 shows a partial cross-section of a first embodiment of a bulkheadand attachment part combination 40 according to the invention andcomprising a bulkhead 50 and an attachment part 60. The bulkhead 50 isformed as a plate with a sandwich construction and comprises a corematerial 52 arranged between a first reinforcement skin 51 arranged at afirst side 54 of the bulkhead 50 and a second reinforcement skin 52arranged at a second side 55 of the bulkhead 50. The bulkhead 50 isattached to the inner shell wall 25 of the wind turbine blade via theattachment part 60. The attachment part 60 comprises a blade wallanchoring part 61 and a bulkhead anchoring part 63, which are connectedby an intermediate part 62 or arm. The bulkhead anchoring part 63 is c-or u-shaped so that it comprises a first part 64 attached to the firstside 54 of the bulkhead 50, a second part 65 attached to the second side55 of the bulkhead, and a third part 66 attached to a circumference 56or edge of the bulkhead 50.

The core material 52 of the bulkhead 50 and the attachment part 60 areadvantageously made of a foamed polyurethane (PUR) material. The foamedPUR may be open-celled or closed-celled, and the core material 52 of thebulkhead 50 may be open-celled, and the attachment part 60closed-celled, or vice versa. PUR is a particular advantageous materialto use, since it is versatile and may be provided in various forms.Thereby, the hardness and flexibility of the material may be varied.However, the attachment part may also be made of a rubber or anotherpolymer material exhibiting similar properties. Thus, the attachmentpart 60 may readily be formed with both an elastomeric part and anon-elastomeric part or a part having less resilience.

In an advantageous embodiment, at least a part of the intermediate part62 of the attachment part 60 is made of an elastomeric material, e.g.having a hardness of 70 on the Shore A scale, whereas the bladeanchoring part 61 and the bulkhead anchoring part 63 may be harder andless resilient. However, in the embodiment shown in FIG. 3, the entireattachment part can be made in the same hardness, since the geometry ofthe attachment part makes the two anchoring parts stiffer. Theelastomeric part of the attachment part 60 ensures easy handling of thebulkhead and attachment part combination 40, when it is mounted in thewind turbine blade. Thus, the flexible attachment part 60 may be foldedinto the opening of the blade root and adhered to the inner shell wall25 of the blade. At the same time the attachment part 60 still providesexcellent strength to carry the bulkhead 50 and a worker standing on thebulkhead 50. Additionally, the elastomeric part of the attachment part60 is able to take up forces from the ovalisation of the root. Theintermediate part 62 may also have a gradually varying hardness or astepwise change in hardness so that an inner part of the intermediatearm 62 (i.e. the part nearest the inner shell wall 25) has a lowerhardness than that of an outer part of the intermediate arm 62.

In the embodiment shown in FIG. 3, the intermediate part 62 of theattachment part 60 is formed as a straight arm extending between theblade anchoring part 61 and the bulkhead anchoring part 63. Theintermediate part forms an angle θ with the inner blade wall 25,advantageously being between 10 and 80 degrees, and more advantageousaround 30-40 degrees. Thereby, the embodiment provides a particularsimple way of obtaining both a longitudinal displacement between theblade anchoring part 61 and the bulkhead anchoring part 63, and adisplacement away from the inner shell wall 25. Thus, the attachmentpart 60 is able to take up forces from the ovalisation of the root aswell as provide the necessary longitudinal or axial strength to carrythe bulkhead 50 and a worker standing on the bulkhead 50.

However, the intermediate arm may in principle form any angle with theinner shell wall. Thus, the intermediate part may for instance extendsubstantially parallel to the inner shell wall with a spacing betweenthe intermediate part and the shell wall as shown in FIG. 4. Theattachment part may even as shown in FIG. 5 be formed so that a part ofthe intermediate part near the blade anchoring part is closer to theblade wall than another part of the intermediate part near the bladewall anchoring part. The intermediate part may also be curved as shownin FIG. 6 or be provided with a bend as shown in FIG. 7.

In another embodiment according to the invention shown in FIG. 8, theblade wall anchoring part, the bulkhead anchoring part and the bulkheadare arranged substantially in the same plane. The blade wall anchoringpart and the bulkhead anchoring part may be connected by a curvedintermediate arm as shown in FIG. 8, or the intermediate arm may extendsubstantially normally to the inner shell wall.

The embodiments shown in FIGS. 3-8 are all formed with a blade anchoringpart, an intermediate part, and a bulkhead anchoring part. However, theattachment part need not comprise an intermediate part as shown in thefollowing embodiments.

As shown in FIG. 9, the attachment part may be formed as a substantiallyuniform ring comprising an elastomeric material, e.g. made of aclosed-celled foamed PUR material. Thus, the ring is made of anelastomeric material which is able to take up forces from theovalisation of the root and carry the bulkhead. The attachment part maybe formed with or without upper and lower legs 81, 82 as depicted inFIG. 9. The attachment part may also be designed with various shapes,e.g. with a substantially triangular cross-section as shown in FIG. 10.To allow the bulkhead's further movement relative to the blade wall, theattachment part need only be adhered to the blade wall at an upper part91 and a lower part 92 of the attachment part. The attachment part maybe provided with a relatively thin, outer shell having a higher hardnessthan the foamed PUR material.

The attachment part may also be formed with a shell and a core part 83as shown in FIG. 11. The core part 83 may in a first embodiment be madeof an open-celled PUR material, which can collapse, thus allowingadditional movement of the bulkhead relative to the inner shell wall ofthe blade. In another embodiment, the core part is made of a material,which is adapted to pulverise or otherwise break apart when subjected toloads, thus forming a hollow part in the attachment part. Thus, the corepart is as such only utilised for obtaining a form-stable shape duringmanufacture (and possibly during mounting) of the bulkhead andattachment part combination. Accordingly, the invention also provides anembodiment having an attachment part comprising a shell with a hollowpart as shown in FIG. 12.

In all the embodiments shown in FIGS. 3-12, the bulkhead anchoring partcomprises a third part which is attached to the circumference of thebulkhead. However, the bulkhead anchoring part may as shown in FIG. 13instead be attached to the first side and the second side of thebulkhead only so that an air gap is formed between the attachment partand the bulkhead, which allows for even further movement of the bulkheadrelative to the shell wall of the blade. This may be applied to all theembodiments shown in FIGS. 3-12. In yet another embodiment, the bladeanchoring part comprises a tongue 85, which is attached to a groove inthe bulkhead as shown in FIG. 14.

The bulkhead and attachment part may be integrally formed. The bulkheadmay for instance be moulded into a PUR cover and with a circumferentialattachment part as shown in FIG. 15. This may in practice be carried outby first manufacturing the bulkhead, e.g. as a circular plate, and thenarranging it in a separate mould and moulding the PUR cover andattachment part onto the bulkhead. In another advantageous embodiment,reinforcement material, such as glass fibres or carbon fibres, ismoulded into a PUR matrix. In yet another embodiment shown in FIG. 16,the bulkhead and attachment part is made in a polymer material only sothat the bulkhead is made in a non-elastomeric polymer material, and theattachment part in an elastomeric material. However, in practice thismakes the bulkhead and attachment part heavy, and accordingly thebulkhead is typically provided with the aforementioned sandwichconstruction or fibre reinforcement so that less material is used andthe bulkhead can be made lighter.

The embodiments shown in FIGS. 3-16 are advantageously formed so thatthe attachment part extends circumferentially around the bulkhead sothat the two parts together seal the root of the blade. However, inanother advantageous embodiment, the attachment part consists of anumber of separate parts 60′, e.g. as shown in FIG. 17. Thus, themodular attachment parts only carry the bulkhead 50′ and areindividually or combined able to take up forces from the ovalisation ofthe root. The blade root may be sealed via a separate seal 90, such as acloth or a separate plate.

According to an advantageous approach, the bulkhead and attachment partcombination is manufactured via the following steps. First, a bulkheadplate is moulded as a sandwich construction by first arranging an innermould between a first layer of glass fibres forming the first skin and asecond layer of glass fibres forming the second skin. An outer mould isclosed around the glass fibres and the inner mould, after which foam isinjected into the inner mould, and finally the sandwich construction iscured or set. If necessary, the shape of the bulkhead is processed, e.g.by cutting, so that the bulkhead fits to the intended blade root.Further, a hole is cut in the plate so as to fit an entry hatch suchthat the internal of the blade can be accessed, once the bulkhead ismounted in the blade root. Then the attachment part is anchored to thebulkhead. This can be carried out by arranging the processed bulkhead inan additional mould and then moulding the attachment part onto thebulkhead. Alternatively, the attachment part may be moulded separatelyand subsequently bonded to the bulkhead. Finally, a hatch is mounted inthe hole in the bulkhead. This can be carried out by first insertingnuts into the bulkhead, e.g. by pressing them into the plate and thenover-laminating them in order to ensure that they are fixed in thebulkhead plate. The hatch can then be mounted in the bulkhead via thenuts. The hatch should be provided with a sealing in order to ensurethat the bulkhead is watertight.

LIST OF REFERENCE NUMERALS

-   2 wind turbine-   4 tower-   6 nacelle-   8 hub-   10 blade-   14 blade tip-   16 blade root-   18 leading edge-   20 trailing edge-   25 inner shell wall/inner blade wall-   30 root region-   32 transition region-   34 airfoil region-   36 shoulder-   40 bulkhead and attachment part combination-   50 bulkhead-   51 first outer skin-   52 core layer-   53 second outer skin-   54 first side of bulkhead-   55 second side of bulkhead-   56 circumference of bulkhead-   60 attachment part-   61 blade wall anchoring part-   62 intermediate part-   63 bulkhead anchoring part-   64 first part of bulkhead anchoring part-   65 second part of bulkhead anchoring part-   66 third part of bulkhead anchoring part-   81 upper leg-   82 lower leg-   83 core part-   84 hollow part-   85 tongue-   90 seal-   91 upper part of attachment part-   92 lower part of attachment part

1. A wind turbine blade (10) having a longitudinal direction (r) with atip end (16) and a root end (14) and a transverse direction, the windturbine blade comprising a blade shell defining a profiled contour ofthe blade and having an inner shell wall (25), wherein the blade (10) isprovided with a bulkhead (50) mounted to the inner shell wall at theroot end of the blade via an attachment part (60), the bulkhead (50)comprising a first side (54) and a second side (55), characterised inthat the attachment part (60) is integrally formed with or connected tothe bulkhead (50), and in that the attachment part (60) comprises anelastomeric material.
 2. A wind turbine blade according to claim 1,wherein the attachment part (60) and the bulkhead (50) together seal theroot end of the blade (10).
 3. A wind turbine blade according to claim1, wherein an outer diameter of the attachment part (60) is equal to orlarger than an inner diameter of the inner shell wall (25).
 4. A windturbine blade according to claim 3, wherein the outer diameter of theattachment part (60) is at least 1 cm, or at least 2 cm, larger than theinner diameter of the inner shell wall (25).
 5. A wind turbine bladeaccording to claim 1, wherein the bulkhead (50) comprises acircumference (56), and the attachment part (60) comprises a blade wallanchoring part (61) and a bulkhead anchoring part (63) attached to thecircumference (56) of the of the bulkhead (50).
 6. A wind turbineaccording to claim 5, wherein the blade wall anchoring part (61) and thebulkhead anchoring part (63) are separated by an intermediate part (62),such as an intermediate arm.
 7. A wind turbine blade according to claim5, wherein the blade wall anchoring part (61), the bulkhead anchoringpart (63) and the bulkhead (50) are arranged substantially in the sameplane.
 8. A wind turbine blade according to claim 5, wherein the bladewall anchoring part (61) and the bulkhead anchoring part (63) aredisplaced along the longitudinal direction of the blade.
 9. A windturbine blade according to claim 8, wherein the blade wall anchoringpart (61) and the bulkhead anchoring part (63) are displaced at least 5cm along the longitudinal direction of the blade, or at least 7.5 cm, orat least 10 cm.
 10. A wind turbine blade according to claim 1, whereinthe bulkhead (50) is displaced at least 2 cm from the inner blade wall(25), or at least 4 cm, or at least 6 cm, when the blade is in anon-ovalised state.
 11. A wind turbine blade according to claim 6,wherein the intermediate arm (62) forms an angle with the inner bladewall (25), the angle lying in an interval of 10 to 80 degrees,advantageously between 10 and 60 degrees, and more advantageouslybetween 10 and 45 degrees, e.g. around 30 degrees.
 12. A wind turbineblade according to claim 6, wherein the intermediate arm (62) isoriented substantially parallel to the longitudinal direction of theblade.
 13. A wind turbine blade according to claim 1, wherein theattachment part (60) comprises a bulkhead anchoring part (63) comprisinga substantially c-shaped or u-shaped part being having a first part (64)attached to the first side (54) of the bulkhead (50) and a second part(65) attached to the second side (55) of the bulkhead (50).
 14. A windturbine blade according to claim 13, wherein the bulkhead anchoring part(63) further has a third part (66) attached to the circumference (56) ofthe bulkhead (50).
 15. A wind turbine blade according to any of claim 1,wherein the bulkhead (50) comprises a circumferential groove and theattachment part (60) is attached to the groove.
 16. A wind turbine bladeaccording to claim 1, wherein the bulkhead (50) is formed as a sandwichconstruction, advantageously comprising a first fibre reinforced skin(51) at the first side (54) of the bulkhead (50), a second fibrereinforced skin (53) at the second side (55) of the bulkhead (50) and acore material (52) between the first skin (51) and the second skin (53).17. A wind turbine blade according to claim 16, wherein the corematerial (52) is made of a polymer material, such as a foamed polymer.18. A wind turbine blade according to claim 17, wherein the elastomericmaterial of the attachment part (60) and the polymer material of thebulkhead (50) are compatible.
 19. A wind turbine blade according toclaim 18, wherein the elastomeric material and the foamed polymer is apolyurethane based material.
 20. A wind turbine blade according to claim1, wherein the attachment part (60) comprises a circumferential hollowpart (84) between the inner blade wall (25) and the bulkhead (50).
 21. Awind turbine blade according to claim 1, wherein the attachment part(60) comprises a circumferential core part (83).
 22. A wind turbineblade according to claim 21, wherein the circumferential core part (83)is made of material, which is adapted to pulverise or otherwise breakapart when subjected to loads.
 23. A wind turbine blade according toclaim 1, wherein the attachment part (60) comprises an elastomeric partand a non-elastomeric part, advantageously both made of polyurethane.24. A wind turbine blade according to claim 23, wherein the elastomericpart of the blade is attached to the inner shell wall (25), and thenon-elastomeric part is attached to the bulkhead (50).
 25. A windturbine blade according to claim 23, wherein the attachment part (60)comprises a gradual transition from an elastomeric material to anon-elastomeric material.
 26. A wind turbine blade according to, whereinthe attachment part comprises a substantially uniform ring having athickness of at least 5 cm, or at least 7 cm, or at least 10 cm.
 27. Awind turbine blade according to claim 1, wherein the elastomericmaterial has a durometer value lying in an interval from 50-100, or50-90, or 55-85 on the Shore A scale, alternatively a durometer valuelying in an interval from 10-50, or 12-40, or 15-30 on the Shore Dscale.
 28. A bulkhead and attachment part combination for a wind turbineblade as described in claim
 1. 29. A method of manufacturing a bulkheadand attachment part, wherein the method comprises the steps of: a)manufacturing a bulkhead, b) manufacturing an attachment part comprisingan elastomeric material, and c) anchoring the attachment part to thebulkhead.
 30. A method according to claim 29, wherein the bulkhead andattachment part are integrally formed.
 31. A method according to claim29, wherein the attachment part is moulded on to the bulkhead, e.g. to acircumference of the bulkhead.
 32. A method according to claim 31,wherein the bulkhead is first shaped and then arranged in a mould so asto mould the attachment part on to the bulkhead.
 33. A method accordingto claim 29, wherein the bulkhead is manufactured as a sandwichconstruction comprising a core material made of a polymer material. 34.A method according to claim 33, wherein the elastomeric material of theattachment part and the core material of the bulkhead are compatible,e.g. chemically compatible.